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rough running zr1

mrmemo

Member
Joined
Feb 12, 2007
Messages
7
Location
Central California
Corvette
1966 silver on silver roadster
I was checking out a 95 zr1 with around 95k miles on it today. the seller said the car had been sitting for a couple of years and that was the reason for the rough idle. he was selling it for a friend and thought it would smooth out as it was driven. it also had a tire sensor light glowing on the dash. he said the car needed to be driven over 50 mph in order for it to reset. Every 4 valve per cylinder car that I have driven were smoother than the 2 valve version of the same car. Are zr1's rough or not? Please advise
 

Aurora40

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Jul 12, 2004
Messages
1,147
Location
The Old Dominion
Corvette
1990 red on red ZR-1
They are not rough. In fact, you can balance a nickel on one in good shape. A car that has been sitting for years could have injector problems. It could also just need a tuneup. My car even had a smoother idle after replacing the PCV valves.

I don't think that's true about the tire pressure sensors but I could be wrong. I believe they work all the time, not just when moving or anything. It could be a battery died in them, who knows.
 

BlackNBlue95

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Joined
Oct 12, 2002
Messages
589
Location
Downers Grove, IL
Corvette
1995 AdmiralBlue LT4/A4
I don't think that's true about the tire pressure sensors but I could be wrong. I believe they work all the time, not just when moving or anything. It could be a battery died in them, who knows.

I believe the C4 TPS are pizoelectric (sp?) so they need to be rolling to produce power. But there still may be something wrong with the system. Many people just disable the LTPWS by pulling the bulb:pat

The rough idle would be a concern, LT5's are expensive motors. I would keep that in thought, there could be many things causing a rough idle...
-=Rick
 

mrmemo

Member
Joined
Feb 12, 2007
Messages
7
Location
Central California
Corvette
1966 silver on silver roadster
I believe the C4 TPS are pizoelectric (sp?) so they need to be rolling to produce power. But there still may be something wrong with the system. Many people just disable the LTPWS by pulling the bulb:pat

The rough idle would be a concern, LT5's are expensive motors. I would keep that in thought, there could be many things causing a rough idle...
-=Rick
thanks for the info. do you know what the life expectancy is for these engines?
 

mrmemo

Member
Joined
Feb 12, 2007
Messages
7
Location
Central California
Corvette
1966 silver on silver roadster
rough idle

They are not rough. In fact, you can balance a nickel on one in good shape. A car that has been sitting for years could have injector problems. It could also just need a tuneup. My car even had a smoother idle after replacing the PCV valves.

I don't think that's true about the tire pressure sensors but I could be wrong. I believe they work all the time, not just when moving or anything. It could be a battery died in them, who knows.

do you know the life expectancy of these engines or what I might expect to spend on rebuilding it? are there any surprises in the price of a tune up?
 

BlackNBlue95

Well-known member
Joined
Oct 12, 2002
Messages
589
Location
Downers Grove, IL
Corvette
1995 AdmiralBlue LT4/A4
do you know the life expectancy of these engines or what I might expect to spend on rebuilding it? are there any surprises in the price of a tune up?


Just like any motor they will last a long time if you take care of them.

Keep in mind LT5 has 16 Fuel Injectors, 2 fuel pumps, and vacum operated secondaries, which use a mechanical vacuum pump to open... they are more complex and more expensive to fix. and if you plan on upgrading it's worse... as far as I know there are no supercharger kits availble.

LT5's are great motors if you have money to burn. Do some research on what a LT5 would cost to replace, or price out some components and compare it to an LT1 or LT4 which performance parts and regular service parts are abundent.
-=Rick
 

Aurora40

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Joined
Jul 12, 2004
Messages
1,147
Location
The Old Dominion
Corvette
1990 red on red ZR-1
thanks for the info. do you know what the life expectancy is for these engines?
I only know what I've heard. They have extremely long lives. I have heard folks mention pulling apart 200k motors that had negligible wear.

http://www.zr1netregistry.com/ZR1_highmileage.htm

Generally it is the stuff bolted to the motor that goes, injectors are a common problem on the 90-92 cars if they don't get driven a lot. Vacuum leaks in the 2ndary system. Then normal C4 stuff, brakes, clutch, whatever.

There have been some folks with headgasket problems, though that has mainly been attributed to using the wrong coolant (DexCool).

I think you would be hard-pressed to find someone who had to have the complete engine replaced because of normal wear/failure. Most likely the rough running is due to things attached to the motor, though you'd certainly want to know the car's history.
 

Aurora40

Well-known member
Joined
Jul 12, 2004
Messages
1,147
Location
The Old Dominion
Corvette
1990 red on red ZR-1
Oh, on the topic of LTPWS, a fair number of people remove them anyway. They are a plastic housing, and are now 12-17 years old. There have been a couple people who have had them break loose in the tire during high-speed driving.

I'd rather just check the pressure regularly than have something like that happen.
 

90 Corvette ZR-1

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Jan 11, 2001
Messages
561
Location
Pittsburgh
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90 Red ZR-1
we have been told that the cars were designed to go somewhere around 400,000 miles between tare downs. yes the lt5 should be very smooth
 

phrogs

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Joined
Dec 25, 2002
Messages
295
Location
Kalamazoo MI
Corvette
90 ZR-1 #854 and 1968 427/400 coupe
If you pass on this deal please let me know the sellers info I am interested in the car.

I need something to build a stroker out of

But to answer one question if you wanted to rebuild the LT5 theres only one guy I know who has all the parts he is a ZR1 fan and owns ZR1s but he is not cheap but since alot of the parts have been discontinued he is the only game in town.

Check ebay out he sells a rebuild kit for $8,000

so if you pass on this car please let me know.

as for the LTPS it is a bad sensor or the signal is blocked going to the reciver or the reciver is bad im going to guess bad wheel sensor and it wont go away by going of 50 mph:boogie



johnny
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
Keep in mind LT5 has 16 Fuel Injectors, 2 fuel pumps, and vacum operated secondaries, which use a mechanical vacuum pump to open... (snip)
-=Rick

There seems to be some confusion about the LT5's secondary port throttles.

Yes, they are vacuum operated but they are operated, for the most part, by manifold vacuum. There is an "auxilary vacuum pump" which acts as an assist during long periods of WOT when the SPT system's vacuum reserviour may become depleated.
 

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